4.1.3. Effect of Material on Surface Carbon Flux

The mass increment, average carbon flux, and segmented average carbon flux changes of three different materials were studied at the carburizing temperatures of 920, 950, and 980 ◦C and carburizing pressures of 100, 200, and 300 Pa to determine the effect of the three carburizing materials on surface carbon flux. Figures 13 and 14 show the effect of carburizing pressure and carburizing temperature on the average carbon flux within 30 s for the three steel materials. 12Cr2Ni4A is indexed as steel #1, 16Cr3NiWMoVNbE as steel #2, and 18Cr2Ni4WA as steel #3.

**Figure 13.** Effect of carburizing pressure on average carbon flux of three materials (**a**) 100 Pa; (**b**) 200 Pa; (**c**) 300 Pa.

**Figure 14.** Effect of carburizing temperature on average carbon flux of three materials in 30s (**a**) 920 ◦C; (**b**) 950 ◦C; (**c**) 980 ◦C.

From the experimental data at the same carburization temperature and pressure, the order of the carbon flux values at 30 s was 12Cr2Ni4A, 18Cr2Ni4WA, and then 16Cr3NiWMoVNbE (without considering diffusion). The average carbon flux is affected by three factors: original carbon content, saturated carbon concentration, and alloy content. The carbon content of 12Cr2Ni4A, 16Cr3NiWMoVNbE, and 18Cr2Ni4WA was 0.12%, 0.16%, and 0.18%, respectively. In terms of alloy elements, 18Cr2Ni4WA has 1% more W than 12Cr2Ni4A, and 16Cr3NiWMoVNbE steel has a more complex alloy system, which contains a large amount of W, Mo, V, and Nb. In the alloy composition of the three materials, Cr, W, Mo, V, and Nb are strong carbide forming elements, whereas Si and Ni are non-carbide forming elements. The alloy content had the greatest effect on carbon flux, followed by the initial carbon concentration, and then saturated carbon concentration. Therefore, 16Cr3NiWMoVNbE steel is more receptive to active carbon atoms.
